DENVER - Former Denver FBI Agent Kevin Knierim says photos and a "bomb fingerprint" could be key to cracking the case of the Boston Marathon bombings.
Knierim sat down with 7NEWS to look at surveillance photos from the bombing. He said some of the photos, which highlight a man in tattered clothing running away, are definitely of interest.
"All of the bystanders (in one photo), and what they're doing is pretty markedly different than this particular person. This could be a disoriented person too, running in an opposite direction for some other reason."
Knierim said another key to cracking the case could be the so-called "bomb fingerprint."
"They can take the way the bomb was made and possibly tie it to the instructions someone may have had or other bombs that have gone off before," he said.
Knierim told 7NEWS no arrests will be made until there is absolute certainty. He also spoke about the errant media reports Wednesday of an arrest that never actually happened, calling it a lesson in caution.
"Every single office in the country is working this, probably 24 hours a day," said Knierim who now owns the private investigation firm Cyopsis. "Nobody wants to miss something or have a detail that was relevant, but wasn't caught."